Safety standards for modern automotive vehicles are becoming increasingly strict. The result of heightened standards and innovations by designers of vehicle restraint systems is twofold: 1) occupants of vehicles are safer and less likely to suffer serious injury in a collision; and 2) manufacturers are held to higher standards with little opportunity to offset costs. As a result of these trends, innovations that increase safety while retaining efficiency and low production costs are essential to manufacturers of related technology.
Presently available motor vehicles include a number of systems designed to provide occupant restraint in a vehicle impact or rollover event. These systems include active seatbelt devices along with passive deployable restraint systems such as driver and passenger-side frontal impact airbags, and side curtain airbags. These systems include a number of deployable elements. In the case of airbags and side curtains, deployable elements include gas generators which produce inflation gas, and may further include additional elements such as controllable vents, tether releases, and other systems. Belt restraint systems also may include deployable elements such as pretensioning systems having micro gas generators, and inflatable seatbelts. A vehicle restraint system controller processes signals from a suite of sensors which enable the detection of a vehicle impact or rollover event. When certain dynamic criteria are present, a deployment command is directed to the various deployable systems. Deployable safety systems have produced significant benefits to occupants in vehicle impact and rollover situations.
Airbag systems typically are composed of a restraint system controller remotely mounted from a reaction canister. The reaction canister contains a folded airbag and an inflator with an initiator (squib). The inflator is connected to the restraint system controller via conductive wires and associated connectors. The total electrical path of these wires and connectors to and from the inflator is termed the “squib loop.” Airbag deployment is commanded when vehicle acceleration sensors measure a threshold sufficient to warrant deployment. Upon this event, a signal is sent to the restraint system controller. The controller then provides sufficient energy to the inflator through the squib loop to initiate the discharge of inflator gas to inflate and deploy the airbag. Other systems including those mentioned previously may also be activated in connection with or instead of airbag deployment.
Historically, airbag safety restraint systems typically employed a single inflator device to release inflation gas for inflating a vehicle occupant restraint airbag in the event of a collision. For these systems, a single pair of connecting wires could be used. In response to increasingly complex performance specifications, inflatable restraint technology has led to the development of what has been termed “adaptive” or “smart” inflator devices and corresponding inflatable restraint systems. One popular adaptation of “smart” systems employs two stages (dual stage system) for inflators that typically utilize two separate initiator assemblies. Some other implementations include a single stage inflator and a tether release, a dual stage inflator (with two initiator connector pockets), and a single stage inflator with an active vent. The present implementations of “smart” systems have varying benefits, but they also have a common characteristic; each requires a multiple stage actuation circuit to actuate the individual devices. These systems are often referred to as duplex systems.
Common implementations of duplex systems utilize separate dedicated wires to activate or perform diagnostics on each individual device. The activation or diagnostic signals are sent from a restraint system controller to each device being commanded. Thus, the evolution of the technology to “smart” and duplex systems has led to an increase in the number of individual firing loops, connectors, output pins, and restraint control module connectors required for providing airbag activation. As a result, such duplex systems typically have larger size, weight, and more complex operation than their single stage counterparts.
In an effort to minimize the complexity and reduce wiring and connection cost, duplex systems have combined multiple firing loops into a single wiring loop path. This design approach is lighter and more efficient in design, but has also introduced some non-linear electrical components in the firing loop to provide for isolation of the individual squibs or other active elements. The additional non-linear components, added to isolate individual squibs or other active elements, can be diodes or other non-linear components. Combining the activation loops has made the “smart” systems require less conducting wire, but current systems remain difficult to assemble and customize for the various devices that may be activated.
As a result of additional control circuitry for the various devices activated using duplex systems, harness assemblies for the various designs are once again becoming increasingly complex. The increased complexity has led to assembly issues and related safety concerns. The aforementioned issues combined with inefficiency due to wasted materials, have resulted in increased manufacturing costs.